Radiology
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Published online before print April 19, 2002, 10.1148/radiol.2233001850
This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
2233001850v1
223/3/780    most recent
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Fenchel, S.
Right arrow Articles by Reske, S. N.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Fenchel, S.
Right arrow Articles by Reske, S. N.
(Radiology 2002;223:780-788.)
© RSNA, 2002

Genitourinary Imaging

Asymptomatic Adnexal Masses: Correlation of FDG PET and Histopathologic Findings1

Sabine Fenchel, MD, Dieter Grab, MD, Karin Nuessle, MD, Joerg Kotzerke, MD, Andrea Rieber, MD, Rolf Kreienberg, MD, Hans-Juergen Brambs, MD and Sven N. Reske, MD

1 From the Departments of Nuclear Medicine (S.F., J.K., S.N.R.), Obstetrics and Gynecology (D.G., R.K.), and Radiology (K.N., A.R., H.J.B.), University of Ulm, Steinhövelstrasse 9, 89075 Ulm, Germany. From the 1999 RSNA scientific assembly. Received November 24, 2000; revision requested January 10, 2001; revision received September 11; accepted October 10. Address correspondence to S.F. (e-mail: sabine.fenchel@medizin.uni-ulm.de).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
PURPOSE: To analyze asymptomatic adnexal masses at positron emission tomography (PET) with fluorodeoxyglucose (FDG) in correlation with histopathologic findings and evaluate FDG PET for assessing malignancy in comparison with transvaginal B-mode and Doppler ultrasonography (US) and magnetic resonance (MR) imaging.

MATERIALS AND METHODS: Ninety-nine patients underwent static FDG PET of the abdomen. US scans were evaluated according to sonomorphologic scoring systems. Resistance index of tumor blood vessels was calculated. Transverse and sagittal T1-weighted MR images obtained before and after intravenous administration of gadopentetate dimeglumine with a fat-saturation technique and T2-weighted MR images were acquired at 1.5 T. Adnexal mass malignancy was first assessed with each modality and then with a combination of the three techniques. Final diagnosis was made with histopathologic evaluation.

RESULTS: FDG PET depicted seven of 12 malignant and 66 of 87 benign asymptomatic adnexal tumors. False-negative PET results were obtained in five of seven stage pT1a cystadenocarcinomas and tumors of low malignant potential but not in advanced-stage ovarian carcinomas. Small moderately intense FDG accumulations in the lower pelvis were caused by benign adnexal tumors or gastrointestinal activity in 21 of 27 cases. The overall sensitivities and specificities were 58% (95% CI: 27.7, 84.8) and 76% (95% CI: 65.5, 84.4), respectively, for FDG PET; 92% (95% CI: 61.5, 99.8) and 60% (95% CI: 48.7, 70.1), respectively, for US; 83% (95% CI: 51.6, 97.7) and 84% (95% CI: 74.5, 90.9), respectively, for MR imaging; and 92% (95% CI: 61.5, 99.8) and 85% (95% CI: 75.8, 91.8), respectively, for the combination of three modalities.

CONCLUSION: Since the sensitivity of US is as high as that of PET, MR imaging, and the combination of three modalities, it remains the method of choice for diagnosis and assessment of asymptomatic adnexal masses.

© RSNA, 2002

Index terms: Ovary, MR, 852.121411, 852.121415, 852.12143 • Ovary, neoplasms, 852.30, 852.311, 852.313, 852.323, 852.324 • Ovary, PET, 852.12163 • Ovary, US, 852.12983, 852.12984, 852.12988, 852.12989 • Positron emission tomography (PET), comparative studies, 852.12163, 852.12166


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Ovarian cancer has the highest mortality of all gynecologic malignancies (1,2). The most important prognostic factor in ovarian cancer is the stage of disease at the time of diagnosis (3). Clinical symptoms at early stages are rare, however, and diagnosis is often made at advanced tumor stages. Screening strategies with tumor markers such as CA-125 are not very effective because of their low sensitivities and specificities (4,5). For example, early-stage ovarian carcinomas and tumors of low malignant potential are often not associated with elevated CA-125 levels, while patients with benign adnexal masses such as endometriomas and inflammatory processes often show increased levels of CA-125 (6,7).

Screening with transvaginal B-mode ultrasonography (US) has led to an increase in the detection of asymptomatic adnexal masses, but a clear differentiation among functional cysts, benign neoplasms, borderline malignancies, and malignant ovarian tumors is often not possible (8–11).

Computed tomography (CT) and magnetic resonance (MR) imaging are established morphologic imaging modalities, though their use in assessing malignancy of adnexal masses, especially small tumor deposits, is limited (8). Advances in MR imaging have led to diagnostic improvements; hence, MR imaging has been proposed as a tool for helping to characterize ovarian masses identified with US but not further classified (12–17).

To date, the method of choice for assessing the malignancy of asymptomatic sonographically suspect adnexal masses is laparoscopy or laparatomy with histopathologic evaluation (10). The disadvantages of this procedure are that if the adnexal tumor is of only functional origin, surgery is unnecessary, but if the adnexal tumor is malignant and is resected with an ovary-conserving procedure, there is the risk of rupturing the tumor capsule and spreading tumor cells into the peritoneal cavity (3,18). Therefore, a noninvasive diagnostic procedure that helps to assess the malignancy of asymptomatic adnexal masses would be clinically useful in deciding the indication for laparoscopy.

Positron emission tomography (PET) with fluorodeoxyglucose (FDG) depicts FDG metabolism and allows diagnosis of malignancy in various types of tumors (19). Suitability of FDG PET for detection of ovarian carcinomas and recurrent disease has already been demonstrated with sensitivities between 83% and 86% (1,20–23). Specificity is more problematic, since only small numbers of benign adnexal masses have been investigated. Specificities range from 54% to 86%, depending on the proportion of inflammatory processes among the benign ovarian lesions (1,22,23). The purposes of this study were to analyze the presentation of asymptomatic adnexal masses at FDG PET in correlation with histopathologic findings and to evaluate the use of FDG PET for assessing the malignancy in comparison with transvaginal B-mode and Doppler US and MR imaging.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Patients
Between May 1997 and February 1999, 99 consecutive patients (age range, 18–83 years; mean age, 46 years ± 15 [SD]) with asymptomatic sonographically suspect (regarded as suspect by the referring physician) adnexal masses were included in this prospective study. The patients were referred to our institution for laparoscopy and within 1 week underwent preoperative FDG PET, transvaginal US, and MR imaging after having given their informed consent. Our study was approved by the institutional ethics committee. The sequencing of the three studies was variable. Within another week, patients underwent laparoscopy. Pregnant women, patients younger than 18 years, and those with clinical symptoms of malignancy were excluded. Final diagnosis was based on histopathologic findings in 97 cases, cytologic findings in one case, and US follow-up in one case.

FDG PET Imaging
PET was performed with scanners (Ecat Exact HR+ and Ecat 931/08/12; CTI-Siemens, Knoxville, Tenn) that produced 63 and 15 transverse sections, respectively, with a section thickness of 2.46 and 6.75 mm, respectively, and covered a transverse field of view of 15.5 and 10.1 cm, respectively. Patients fasted at least 6 hours before the examination. Fifty minutes after intravenous injection of 222–555 MBq of FDG, static emission scans of the abdomen (usually three contiguous bed positions), with an acquisition time of 12 minutes per bed position, were obtained. Diuresis was stimulated with an intravenous injection of 20 mg of furosemide (Lasix; Aventis, Frankfurt, Germany) and oral hydration. PET images were reconstructed iteratively according to Schmidlin and Doll (24). Transmission scans were not obtained.

PET images were interpreted visually in consensus in transaxial, coronal, and sagittal sections by two or three experienced nuclear medicine physicians (S.F., J.K., S.N.R.), who had no knowledge of patients’ clinical or other imaging data. In difficult cases, maximum intensity projections in the cine mode were also evaluated. FDG accumulations in the adnexal region that were as intense as or more intense than the physiologic liver uptake and could not be attributed to structures such as the bladder, the ureters, or the gastrointestinal tract, which physiologically accumulate FDG, were considered positive for malignancy. Curved, nonfocal, and moderately intense FDG accumulations that projected into the gastrointestinal tract were considered to represent physiologic gastrointestinal activity.

The intensity of FDG uptake in the adnexal region was graded subjectively on a five-point scale as follows: 1, no FDG uptake; 2, less than liver FDG uptake; 3, FDG uptake as intense as the corresponding physiologic liver uptake; 4, moderately intense FDG uptake; and 5, intense FDG uptake. Intensity of liver uptake was graded as in the middle of the five-point scale. There were two intensity classes below and two above the intensity of liver uptake.

After the first blinded interpretation of PET images, a second evaluation was performed with MR images (no coregistration) to correlate the physiologic information obtained at PET with the anatomic information obtained at MR imaging.

US Scanning
Transvaginal US (Combison 530; Kretztechnik, Marl, Germany) was performed by using a 240° real-time sector transducer with a frequency of 7.5 MHz. The endovaginal probe was equipped with B-mode, color Doppler, and pulsed Doppler imaging. The adnexal region was evaluated by one experienced gynecologist (D.G.), without knowledge of clinical or other imaging data, according to the morphologic index proposed by DePriest et al (25) and the sonomorphologic classification published by Kawai et al (26) (Tables 1, 2). In addition, tumor vessels were visualized at color Doppler US, and the resistance index was calculated as maximum systolic velocity minus maximum end-diastolic velocity divided by maximum systolic velocity by using pulsed Doppler US. If more than one tumor vessel could be visualized, the lowest resistance index was used for further analysis. Adnexal masses with a DePriest et al score of greater than or equal to 5, a score of 9–12 according to the Kawai et al classification, or a resistance index of less than 0.45 were considered malignant.


View this table:
[in this window]
[in a new window]

  		TABLE 1. Morphology Index according to DePriest et al

 

View this table:
[in this window]
[in a new window]

  		TABLE 2. Sonomorphologic Classification according to Kawai et al

 
MR Imaging
MR imaging of the lower abdomen was performed with a 1.5-T MR unit (Magnetom Vision; Siemens, Erlangen, Germany) by using a dedicated body-array coil with a breath-hold technique. Transverse and sagittal T1-weighted flash two-dimensional images (79.2/4.1 [repetition time msec/echo time msec] and 72.5/4.1, respectively; flip angle, 70°; section thickness, 6 mm; field of view, 300 mm; matrix, 101 x 256 and 121 x 256, respectively) were acquired before and after intravenous administration of gadopentetate dimeglumine (Magnevist; Schering, Berlin, Germany) at a standard dose of 0.1 mmol per kilogram of body weight. In 78 patients, contrast material–enhanced T1-weighted sequences (89.3/4.1; flip angle, 70°; section thickness, 6 mm; field of view, 300 mm; matrix, 88 x 256) were performed by using a fat-saturation technique. In addition, transverse and sagittal T2-weighted turbo spin-echo sequences (2,800/138; flip angle, 180°; section thickness, 6 mm; field of view, 300 mm; matrix, 116 x 256) were performed.

Images were evaluated by two experienced radiologists (K.N., A.R.) without knowledge of clinical or other imaging data. Any solid adnexal masses with contrast medium uptake and cystic adnexal masses with septa of more than 3-mm wall thickness or with solid parts were considered positive for malignancy. Solid adnexal masses without contrast medium uptake and cystic adnexal masses with septa of less than 3-mm wall thickness and without solid parts were considered benign. Further criteria for malignancy were peritoneal, mesenteric, or omental disease manifestations; lymphomas; or ascites.

Data Analyses
For each imaging technique (FDG PET, US, and MR imaging), sensitivity, specificity, positive and negative predictive values, accuracy, and 95% CIs were independently calculated. Images acquired with all three modalities were reviewed with consensus by one nuclear medicine specialist (S.F.), two radiologists (K.N., A.R.), and one gynecologist (D.G.), and a final assessment of malignancy of the adnexal masses was made. Sensitivity, specificity, positive and negative predictive values, accuracy, and 95% CIs were then calculated for the combination of the three methods. The reviewers had no information about patient’s age, physical examination, tumor markers, and surgical or histopathologic findings.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 
Of 99 patients with asymptomatic pelvic masses, 12 (12%) had malignant ovarian tumors: seven adenocarcinomas (stage pT1a, three cases; stage pT3b, one case; stage pT3c, three cases), four ovarian tumors of low malignant potential, and one instance of metastatic breast cancer. In 87 (88%) patients, the ovarian tumors were benign and included inflammatory tumors (six cases), benign solid tumors (seven cases), cystadenomas (12 cases), serous cysts (10 cases), dermoid cysts (seven cases), corpus luteum cysts (five cases), hydrosalpinges (seven cases), endometriomas (23 cases), and other entities (10 cases; one case of a simple cyst was verified at cytologic analysis and one case of a functional cyst, at follow-up).

FDG PET Imaging
Visual interpretation of the PET images allowed correct classification of seven of the 12 malignant tumors (Fig 1). False-negative PET results were obtained in two stage pT1a cystadenocarcinomas and in three tumors of low malignant potential. Findings in all five false-negative cases showed slightly elevated glucose uptake in the tumor region, but the FDG accumulation could not be clearly attributed to tumor tissue or physiologic gastrointestinal activity. Of the 87 functional or benign ovarian masses, 66 were true-negative at FDG PET. False-positive PET results were obtained in 21 pelvic tumors. Intense glucose metabolism was found in all four acute inflammatory processes (Fig 2), one benign schwannoma, and one of five corpus luteum cysts. Moderately intense FDG accumulations were seen in one teratoma, in the septa of one cystadenoma, and in one endometrioma. When PET images in these patients were interpreted retrospectively with MR images, the FDG accumulations could clearly be attributed to solid tumor tissue.



View larger version (148K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 1. A, Transverse and B, sagittal FDG PET images of stage pT3c ovarian adenocarcinoma. The intense FDG uptake of the tumor bulk (arrowheads) and the peritoneal metastases (large arrows) are characteristic of malignancy. The small arrow demonstrates activity in the urinary bladder. C, Transvaginal sonogram shows large irregulary solid patterns (arrowhead) with irregulary cystic parts (arrow). D, Corresponding sagittal T1-weighted two-dimensional gadolinium-enhanced MR image (72.5/4.1; flip angle, 70°) shows the tumor bulk (arrowhead) and the peritoneal metastases (arrow).

 


View larger version (68K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 2. A, Coronal and B, transverse FDG PET images of an inflammatory tumor (salpingitis) (arrows) in the left lower pelvis demonstrate the typical intense FDG metabolism of inflammations.

 
False-positive PET findings that resulted from intense or moderately intense FDG accumulations were found in one serous cyst, one multilocular mucinous cystadenoma, one dermoid cyst, one corpus luteum cyst, one hydrosalpinx, and one endometrioma. Retrospective comparison of PET images with MR images showed that FDG accumulations could be attributed to physiologic gastrointestinal activity and were not due to elevated tumoral FDG uptake.

False-positive FDG accumulations were found in one benign thecoma, three endometriomas, one tumor of granulation tissue, and one conglomerate tumor of adhesions. In these cases, retrospective review of the PET images and comparison with MR images did not result in a clear differentiation between physiologic gastrointestinal FDG metabolism and tumoral FDG accumulation.

A total of 23 endometriomas were identified. While elevated FDG metabolism in the tumor region was observed in five (22%) cases, no elevated glucose metabolism could be found in 18 (78%) endometriomas (Fig 3). When PET images of these five cases were compared with MR images, the elevated glucose metabolism could clearly be attributed to the endometrioma in only one case, but in one case, the FDG accumulation was clearly caused by gastrointestinal activity. In the three remaining cases, a clear differentiation between gastrointestinal activity and tumoral FDG uptake was not possible.



View larger version (49K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3. A, Coronal and B, transverse FDG PET images of a cystic endometrioma (arrows). Like most endometriomas, the cystic tumor presents as a photopenic defect without elevated FDG uptake in the interior of the cyst or in the tumor wall. The tumor is surrounded by gastrointestinal activity (arrowheads), which demonstrates the typical curved nonfocal configuration of physiologic gastrointestinal activity. C, Corresponding transverse T2-weighted turbo spin-echo MR image (2,800/138 msec; flip angle, 180°) of the cystic endometrioma (arrow). D, Transvaginal sonogram shows a single-chambered cyst with multiple linear echos (according to Kawai et al, score 6) and a papillary wall structure (according to DePriest et al, score 3) (arrow).

 
Overall sensitivity and specificity of FDG PET for detection of malignant ovarian masses were 58% (95% CI: 27.7, 84.8) and 76% (95% CI: 65.5, 84.4), respectively. Positive predictive value, negative predictive value, and accuracy were 25% (95% CI: 10.7, 44.9), 93% (95% CI: 84.3, 97.9), and 74% (95% CI: 63.9, 82.1), respectively.

US Scanning
Transvaginal US, in which two sonomorphologic scoring systems and Doppler flow measurements were used, depicted 11 of 12 malignant ovarian tumors (true-positive findings), resulting in a sensitivity of 92% (95% CI: 61.5, 99.8), and 52 of 87 benign ovarian masses (true-negative findings), resulting in a specificity of 60% (95% CI: 48.7, 70.1). The single false-negative result was obtained in a polycystic tumor with low malignant potential that showed no solid parts. False-positive classifications were made in four of six inflammatory tumors, three of seven benign solid tumors, nine of 12 cystadenomas, two of seven dermoid cysts, four of five corpus luteum cysts, two of 15 simple cysts, three of seven hydrosalpinges, five of 23 endometriomas, and three other tumor entities. The positive predictive value, negative predictive value, and accuracy were 24% (95% CI: 12.6, 38.8), 98% (95% CI: 89.9, 100), and 64% (95% CI: 53.4, 73.1), respectively.

MR Imaging
MR imaging correctly depicted 10 of 12 malignant ovarian tumors and 73 of 87 benign ovarian lesions, resulting in a sensitivity of 83% (95% CI: 51.6, 97.9) and a specificity of 84% (95% CI: 74.5, 90.9). False-negative results in our patient group were obtained in a polycystic tumor with low malignant potential and one stage pT3b ovarian carcinoma. False-positive classifications were made in two of six inflammatory tumors, two of seven benign solid tumors, two of 12 cystadenomas, three of five corpus luteum cysts, two of 15 simple cysts, one of seven hydrosalpinges, and two other tumor entities. Positive predictive value, negative predictive value, and accuracy were 42% (95% CI: 24.4, 65.1), 97% (95% CI: 90.7, 99.7), and 84% (95% CI: 75.1, 90.5), respectively.

FDG PET, US, and MR Imaging
A final consensus interpretation, in which the malignancy of ovarian tumors was assessed with the review of FDG PET, US, and MR findings, resulted in true-positive diagnoses in 11 of 12 cases of malignant disease (sensitivity 92%; 95% CI: 61.5, 99.8) and true-negative diagnoses in 74 of 87 cases of benign disease (specificity 85%; 95% CI: 75.8, 91.8). Positive predictive value, negative predictive value, and accuracy for the combination of the three imaging modalities were 46% (95% CI: 25.5, 67.2), 99% (95% CI: 92.8, 100), and 86% (95% CI: 77.4, 92.0), respectively.

Table 3 presents the diagnoses, as well as PET, US, and MR results, in the 99 patients. Sensitivity, specificity, positive and negative predictive values, as well as the accuracy of the three imaging modalities, are given in Table 4.


View this table:
[in this window]
[in a new window]

  		TABLE 3. Diagnoses and FDG PET, US, and MR Imaging Results in 99 Patients

 

View this table:
[in this window]
[in a new window]

  		TABLE 4. Statistical Results

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
REFERENCES
 
The use of transvaginal US as a screening strategy in gynecology has led to an increase in the detection of asymptomatic adnexal masses, which can be found with US in about 10% of premenopausal women (27,28). However, assessment of malignancy in these adnexal masses with clinical investigation and B-mode US is often uncertain. Therefore, we investigated whether FDG PET, MR imaging, and transvaginal B-mode, color Doppler, and pulsed Doppler US can help improve the assessment of malignancy.

Our patient group consisted of 12 (12%) patients with malignant and 87 (88%) patients with benign ovarian tumors of different histologic characterisitcs; hence, the patient population was representative of actual patients with asymptomatic adnexal masses (27). Among malignant ovarian lesions, we found only a low proportion (four of 12) of advanced ovarian carcinomas (stage pT3) and a high proportion (seven of 12) of tumors of low malignant potential and early-stage ovarian carcinomas, which can be explained by the fact that only asymptomatic patients were examined.

In our study, FDG PET had a sensitivity of 58% (95% CI: 27.7, 84.8) in depicting malignant ovarian lesions, which is probably lower than that in other studies in which sensitivities between 83% and 86% were reported (1,22,23). One probable reason is the high percentage of tumors of low malignant potential and early-stage ovarian carcinomas among the malignant ovarian lesions in contrast to other studies with a high proportion of advanced-stage tumors. While all four advanced ovarian carcinomas showed elevated glucose metabolism and were correctly classified as true-positive at FDG PET (Fig 1), only two of seven tumors of low malignant potential and early-stage ovarian carcinomas were interpreted as malignant on the basis of an elevated FDG uptake in the tumor region. The limited detection rate of tumors of low malignant potential and early-stage ovarian carcinomas at FDG PET can be explained by the low mass of malignantly transformed tissue in these tumors. The limited resolution of FDG PET and the partial volume effect may prevent visualization of such small tumor deposits despite their potential accumulation of FDG. One further explanation for the low detection rate of tumors of low malignant potential and early-stage carcinomas might be the different degree of malignant cell transformation in these tumors and the possible lack of elevated glucose metabolism. The high sensitivity of FDG PET in depicting advanced ovarian carcinomas and recurrent ovarian carcinomas as outlined in the literature (1,22,23) remains unquestioned.

In accordance with the literature, specificities of FDG PET in the assessment of adnexal masses range from 54% to 86% (1,22,23). These values, however, are based on small numbers of benign adnexal masses (n = 18, 13, and seven, respectively) and are influenced by the proportion of inflammatory processes, which usually also have a markedly elevated glucose metabolism (1,22,23,29). In our study, we investigated 87 benign ovarian masses with a specificity of 76% (95% CI: 65.5, 84.4). False-positive results were obtained in histologically different tumor entities.

All four acute inflammatory processes were misclassified as false-positive at FDG PET because of their high FDG metabolism (Fig 2). Similar results are described by Romer et al (22) for one abscess of the ovary and by Zimny et al (23) for one case of salpingo-oophoritis and one case of local peritonitis. These results show that the intensitiy of glucose metabolism as the only criterion for differentiating ovarian malignancies from acute inflammatory processes of the ovary is insufficient. Whether morphologic aspects might be helpful in differential diagnosis should be investigated in appropriate studies.

Elevated FDG accumulation in endometriomas has been described in the literature in few cases (1,22). In our study, the typical appearance of a cystic endometrioma, as shown in Figure 3, was a photopenic defect without FDG accumulation in the interior or the wall of the cystic tumor. Moderately intense FDG accumulations in the tumor region were found in five (22%) of 23 cases. Moreover, in the retrospective review of PET and MR images, elevated FDG metabolism could be clearly attributed to the tumor mass in one case; whereas in one case, the FDG accumulation was caused by adjacent physiologic gastrointestinal activity, while in three other cases, gastrointestinal activity could not be differentiated from tumoral FDG uptake. These results show that endometriomas usually do not exhibit elevated FDG metabolism.

Glucose metabolism in schwannomas has been described in only a few cases. In accordance with the false-positive FDG PET result in a thoracic schwannoma reported by Knight et al (30) and the moderately intense FDG accumulation in a mediastinal schwannoma reported by Kubota et al (31), schwannoma of the lower pelvis in our study presented as an intense FDG-accumulating tumor and was therefore misclassified as false-positive.

Concerning the FDG metabolism of corpus luteum cysts, our results support the findings of Zimny et al (23) that these cysts can show an elevated, as well as a normal, glucose metabolism. The reasons for these differences in glucose metabolism are not known. Inflammatory processes in the tumor area at the time of PET imaging could be an explanation.

In accordance with the results of other investigators, the mature teratoma in our study showed a moderately intense glucose metabolism (32–35). Further moderate FDG accumulations were observed in the solid parts and septa of one mucinous cystadenoma.

In contrast to the cases in which FDG metabolism could be clearly attributed to solid tumor tissue, the retrospective review of PET and MR images showed that in six cases (one serous cyst, one mucinous cystadenoma, one dermoid cyst, one corpus luteum cyst, one hydrosalpinx, and one endometrioma), the elevated FDG uptake in the tumor region was caused by physiologic gastrointestinal activity, while in six cases (one benign thecoma, three endometriomas, one tumor of granulation tissue and one conglomerate tumor of adhesions), review of PET and MR images did not permit a clear distinction between elevated tumoral FDG metabolism and physiologic gastrointestinal activity (Table 1).

These results underscore a general disadvantage of FDG PET: its difficulty in differentiating physiologic gastrointestinal activity from FDG accumulation in tumor tissue in the lower pelvis. Intensity of glucose metabolism alone is not sufficient as the only differential criterion, since glucose metabolism in the gastrointestinal tract can sometimes reach the same intensity as the glucose metabolism in malignant tumors. If FDG accumulations have the typical curved nonfocal configuration of gastrointestinal activity shown in Figure 3, they can be easily attributed to the gastrointestinal tract, but difficulties arise when moderately intense FDG accumulations must be interpreted in the absence of this typical curved configuration. Attribution of these FDG accumulations to anatomic structures on functionally oriented transverse, coronal, and sagittal PET images is often uncertain. Maximum intensity projections in the cine mode, which lead to a three-dimensional image impression, or comparison of PET images with morphologically oriented imaging modalities such as MR imaging can improve anatomic localization of FDG accumulations and thus improve specificity of PET, especially in the lower pelvis, and must be used in cases of unclear FDG accumulations.

The data of our study show that nonfocal moderately intense FDG accumulations in the lower pelvis are usually caused by physiologic gastrointestinal activity or benign ovarian tumors, and only in rare cases, by malignant ovarian lesions. However, constant interpretation of moderately intense FDG accumulations in the lower pelvis as benign would lead to a loss of sensitivity of FDG PET in depicting malignant ovarian tumors, since moderate FDG accumulations can represent an elevated FDG metabolism in tumors of low malignant potential and early-stage ovarian carcinomas.

Concerning malignant ovarian tumors, it can be concluded that ovarian malignancies usually exhibit high FDG metabolism and can be visualized as intense FDG accumulations at PET if they have reached a certain critical tumor mass. However, detection of tumors of low malignant potential and early-stage ovarian carcinomas at FDG PET is limited, probably because of the low mass of malignantly transformed tumor tissue. Unfortunately, in regard to a patient’s prognosis, detection of these early tumor stages is clinically essential.

For the assessment of malignancy in asymptomatic sonographically suspect adnexal masses, the ideal method should reach a high specificity because of the low incidence of ovarian malignancies. Yet FDG PET with a specificity of 76% (95% CI: 65.5, 84.4) and a negative predictive value of 93% does not fulfill this requirement. All in all, the suitability of FDG PET in the assessment of malignancy in asymptomatic sonographically suspect adnexal masses is limited.

US is said (13) to be a sensitive but nonspecific tool for classification of asymptomatic adnexal masses. Sensitivities of 74%–100% have been described, depending on the imaging technique and the use of different scoring systems (4–6,17,36–42). Doppler sonography is not believed to improve sensitivity (5,36,42,43). In our study, which combined sonomorphologic scoring systems of DePriest et al (25) and Kawai et al (26) and Doppler flow measurements of tumor vessels, we reached a sensitivity of 92% (95% CI: 61.5, 99.8), which is in accordance with the results described in literature. Concerning the specificity of US for helping to assess the malignancy of adnexal masses, values from 40% to 87% are described (4–6,36,37,39,40,42–44). In our own study, specificity was 60% (95% CI: 48.7, 70.1), which is in accordance with these results. Concerning the overall value of US in helping to assess malignancy in asymptomatic adnexal masses, our study findings confirm that transvaginal US, in which sonomorphologic scoring systems and Doppler flow measurements are used, is a very sensitive method but has only low specificity, which leads to many false-positive results.

MR imaging, as the third imaging modality investigated for the assessment of malignancy in adnexal masses, is associated in literature with sensitivities of 49%–100%, specificities of 97%–98%, and accuracies of 70%–99%, depending on the patient group and the imaging technique (6,6,41,42,45–47). Sensitivity, specificity, and accuracy of 83% (95% CI: 51.6, 97.9), 84% (95% CI: 74.5, 90.9), and 84% (95% CI: 75.1, 90.5), respectively, for MR imaging in our study are in agreement with these results.

Sensitivities of FDG PET, US, MR imaging, and the combination of these techniques in our study should not be used for the final comparison, since the number of malignant ovarian lesions investigated was small (n = 12) and resulted in wide-ranged and overlapping 95% CIs.

Concerning specificities in the assessment of asymptomatic adnexal masses, findings from MR imaging and the combination of the three imaging techniques showed statistically higher specificities than US. Specificity of FDG PET was not statistically different from that of US, MR imaging, and the combination of the three imaging techniques. Addition of MR imaging or MR imaging and PET to US thus leads to a reduction in false-positive results in the assessment of the malignancy of adnexal masses, yet sensitivity of US does not seem to improve significantly.

The important general advantages of US compared with PET and MR imaging include patient comfort, availability, and low costs. Furthermore, the sensitivity of a careful US examination does not seem to improve significantly by the addition of PET and MR imaging examinations. Therefore, the use of US as the most important diagnostic tool in the detection and assessment of asymptomatic adnexal masses remains unchallenged. FDG PET and MR imaging in addition to US can provide further information about tumor entity and improve specificity. The modalities may be useful in selected cases but cannot be recommended in general. From the oncologic point of view, all sonographically suspect adnexal masses require surgery and thorough histopathologic evaluation.


   FOOTNOTES
 
Abbreviation: FDG = fluorodeoxyglucose

Author contributions: Guarantors of integrity of entire study, S.F., D.G., K.N., A.R., R.K., H.J.B., S.N.R.; study concepts and design, D.G.; literature research, D.G., S.F.; clinical studies, K.N., D.G., S.F.; data acquisition, D.G., K.N., A.R., S.F.; data analysis/interpretation, D.G., K.N., A.R., J.K., S.N.R., S.F.; statistical analysis, S.F.; manuscript preparation and editing, S.F.; manuscript definition of intellectual content, D.G., K.N., A.R., S.F.; manuscript revision/review, D.G., K.N., J.K., A.R., R.K., H.J.B., S.N.R.; manuscript final version approval, all authors.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 

  1. Hubner KF, McDonald TW, Niethammer JG, Smith GT, Gould HR, Buonocore E. Assessment of primary and metastatic ovarian cancer by positron emission tomography (PET) using 2-[18F]deoxyglucose (2-[18F]FDG). Gynecol Oncol 1993; 51:197-204.[CrossRef][Medline]
  2. Maiman M. Laparoscopic removal of the adnexal mass: the case for caution. Clin Obstet Gynecol 1995; 38:370-379.[CrossRef][Medline]
  3. Osmers R. Sonographic evaluation of ovarian masses and its therapeutical implications. Ultrasound Obstet Gynecol 1996; 8:217-222.[CrossRef][Medline]
  4. Alcazar JL, Errasti T, Zornoza A, Minguez JA, Galan MJ. Transvaginal color Doppler ultrasonography and CA-125 in suspicious adnexal masses. Int J Gynaecol Obstet 1999; 66:255-261.[CrossRef][Medline]
  5. Franchi M, Beretta P, Ghezzi F, Zanaboni F, Goddi A, Salvatore S. Diagnosis of pelvic masses with transabdominal color Doppler, CA 125 and ultrasonography. Acta Obstet Gynecol Scand 1995; 74:734-739.[Medline]
  6. Komatsu T, Konishi I, Mandai M, et al. Adnexal masses: transvaginal US and gadolinium-enhanced MR imaging assessment of intratumoral structure. Radiology 1996; 198:109-115.[Abstract/Free Full Text]
  7. Jacobs I, Bast R. The CA125 tumor associated antigen: a review of the literature. Hum Reprod 1989; 4:1-12.[Abstract/Free Full Text]
  8. Bragg DG, Hricak H. Imaging in gynecologic malignancies. Cancer 1993; 71(4 suppl):1648-1651.[Medline]
  9. Magrina JF, Cornella JL. Office management of ovarian cysts. Mayo Clin Proc 1997; 72:653-656.[Abstract]
  10. Minelli L. Ovarian cysts. Eur J Obstet Gynecol Reprod Biol 1996; 65:81-89.[CrossRef][Medline]
  11. Van VP, Massuger LF, Ruys SH, Barentsz JO. Borderline ovarian malignancy: ultrasound and fast dynamic MR findings. Eur J Radiol 1998; 28:136-142.[CrossRef][Medline]
  12. Yamashita Y, Torashima M, Hatanaka Y, et al. Adnexal masses: accuracy of characterization with transvaginal US and precontrast and postcontrast MR imaging. Radiology 1995; 194:557-565.[Abstract/Free Full Text]
  13. Outwater EK, Dunton CJ. Imaging of the ovary and adnexa: clinical issues and applications of MR imaging. Radiology 1995; 194:1-18.[Abstract/Free Full Text]
  14. Outwater EK, Schiebler ML. Magnetic resonance imaging of the ovary. Magn Reson Imaging Clin N Am 1994; 2:245-274.[Medline]
  15. Hamm B, Kubik-Huch RA, Fleige B. MR imaging and CT of the female pelvis: radiologic-pathologic correlation. Eur Radiol 1999; 9:3-15.[CrossRef][Medline]
  16. Jain KA, Jeffrey RBJ. Evaluation of pelvic masses with magnetic resonance imaging and ultrasonography. J Ultrasound Med 1994; 13:845-853.[Abstract]
  17. Semelka RC, Lawrence PH, Shoenut JP, Heywood M, Kroeker MA, Lotocki R. Primary ovarian cancer: prospective comparison of contrast-enhanced CT and pre-and postcontrast, fat-suppressed MR imaging, with histologic correlation. J Magn Reson Imaging 1993; 3:99-106.[Medline]
  18. Osmers RG, Osmers M, von MB, Wagner B, Kuhn W. Preoperative evaluation of ovarian tumors in the premenopause by transvaginosonography. Am J Obstet Gynecol 1996; 175:428-434.[CrossRef][Medline]
  19. Reske SN, Bares R, Bull U, Guhlmann A, Moser E, Wannenmacher MF. Clinical value of positron emission tomography (PET) in oncologic questions: results of an interdisciplinary consensus conference. Schirmerreschaft der Deutschen Gesellschaft for Nuklearmedizin. Nuklearmedizin 1996; 35:42-52[German].
  20. Casey MJ, Gupta NC, Muths CK. Experience with positron emission tomography (PET) scans in patients with ovarian cancer. Gynecol Oncol 1994; 53:331-318.[CrossRef][Medline]
  21. Karlan BY, Hawkins R, Hoh C, et al. Whole-body positron emission tomography with 2-[18F]-fluoro-2-deoxy-D-glucose can detect recurrent ovarian carcinoma. Gynecol Oncol 1993; 51:175-181.[CrossRef][Medline]
  22. Romer W, Avril N, Dose J, et al. Metabolic characterization of ovarian tumors with positron-emission tomography and F-18 fluorodeoxyglucose. Rofo Fortschr Geb Rontgenstr Neuen Bildgeb Verfahr 1997; 166:62-68[German].[Medline]
  23. Zimny M, Schroder W, Wolters S, Cremerius U, Rath W, Bull U. 18F-fluorodeoxyglucose PET in ovarian carcinoma: methodology and preliminary results. Nuklearmedizin 1997; 36:228-233[German].[Medline]
  24. Schmidlin P, Doll J. Implementation of iterative reconstruction in positron emission tomography. Prog Clin Biol Res 1991; 363:59-67.[Medline]
  25. DePriest PD, Shenson D, Fried A, et al. A morphology index based on sonographic findings in ovarian cancer. Gynecol Oncol 1993; 51:7-11.[CrossRef][Medline]
  26. Kawai M, Kano T, Kikkawa F, Maeda O, Oguchi H, Tomoda Y. Transvaginal Doppler ultrasound with color flow imaging in the diagnosis of ovarian cancer. Obstet Gynecol 1992; 79:63-67.
  27. Tanos V, Schenker JG. Ovarian cysts: a clinical dilemma. Gynecol Endocrinol 1994; 8:59-67.[Medline]
  28. Borgfeld C, Andolf E. Transvaginal sonographic ovarian findings in a random sample of woman 25–40 years old. Ultrasound Obstet Gynecol 1999; 13:345-350.[CrossRef][Medline]
  29. Kubota R, Yamada S, Kubota K, Ishiwata K, Tamahashi N, Ido T. Intratumoral distribution of fluorine-18-fluorodeoxyglucose in vivo: high accumulation in macrophages and granulation tissues studied by microautoradiography. J Nucl Med 1992; 33:1972-1980.[Abstract/Free Full Text]
  30. Knight SB, Delbeke D, Stewart JR, Sandler MP. Evaluation of pulmonary lesions with FDG-PET: comparison of findings in patients with and without a history of prior malignancy. Chest 1996; 109:982-988.[Abstract/Free Full Text]
  31. Kubota K, Yamada S, Kondo T, et al. PET imaging of primary mediastinal tumours. Br J Cancer 1996; 73:882-886.[Medline]
  32. Bender H, Schomburg A, Albers P, Ruhlmann J, Biersack HJ. Possible role of FDG-PET in the evaluation of urologic malignancies. Anticancer Res 1997; 17:1655-1660.[Medline]
  33. Reinhardt MJ, Muller-Mattheis VG, Gerharz CD, Vosberg HR, Ackermann R, Muller-Gartner HW. FDG-PET evaluation of retroperitoneal metastases of testicular cancer before and after chemotherapy. J Nucl Med 1997; 38:99-101.[Abstract/Free Full Text]
  34. Stephens AW, Gonin R, Hutchins GD, Einhorn LH. Positron emission tomography evaluation of residual radiographic abnormalities in postchemotherapy germ cell tumor patients. J Clin Oncol 1996; 14:1637-1641.[Abstract/Free Full Text]
  35. Wilson CB, Young HE, Ott RJ, et al. Imaging metastatic testicular germ cell tumours with 18FDG positron emission tomography: prospects for detection and management. Eur J Nucl Med 1995; 22:508-513.[Medline]
  36. Valentin L. Prospective cross-validation of Doppler ultrasound examination and gray-scale ultrasound imaging for discrimination of benign and malignant pelvic masses. Ultrasound Obstet Gynecol 1999; 14:273-283.[CrossRef][Medline]
  37. Merz E, Weber G, Bahlmann F, Kiesslich R. A new sonomorphologic scoring system (Mainz Score) for assessment of ovarian tumors using transvaginal ultrasonography. Ultraschall Med 1998; 19:99-107.[Medline]
  38. DePriest PD, Varner E, Powell J, et al. The efficacy of a sonographic morphology index in identifying ovarian cancer: a multi-institutional investigation. Gynecol Oncol 1994; 55:174-178.[CrossRef][Medline]
  39. Sassone AM, Timor-Tritsch IE, Artner A, Westhoff C, Warren WB. Transvaginal sonographic characterization of ovarian disease: evaluation of a new scoring system to predict ovarian malignancy. Obstet Gynecol 1991; 78:70-76.[Medline]
  40. Benacerraf BR, Finkler NJ, Wojciechowski C, Knapp RC. Sonographic accuracy in the diagnosis of ovarian masses. J Reprod Med 1990; 35:491-495.[Medline]
  41. Jain KA, Friedman DL, Pettinger TW, Alagappan R, Jeffrey RBJ, Sommer FG. Adnexal masses: comparison of specificity of endovaginal US and pelvic MR imaging. Radiology 1993; 186:697-704.[Abstract/Free Full Text]
  42. Hata K, Hata T, Manabe A, Sugimura K, Kitao M. A critical evaluation of transvaginal Doppler studies, transvaginal sonography, magnetic resonance imaging, and CA 125 in detecting ovarian cancer. Obstet Gynecol 1992; 80:922-926.[Medline]
  43. Stein SM, Laifer-Narin S, Johnson MB, et al. Differentiation of benign and malignant adnexal masses: relative value of gray-scale, color Doppler, and spectral Doppler sonography. AJR Am J Roentgenol 1995; 164:381-386.[Abstract/Free Full Text]
  44. Ferrazzi E, Zanetta G, Dordoni D, et al. Transvaginal ultrasonographic characterization of ovarian masses: comparison of five scoring systems in a multicenter study. Ultrasound Obstet Gynecol 1997; 10:192-197.[CrossRef][Medline]
  45. Kurtz AB, Tsimikas JV, Tempany CM, et al. Diagnosis and staging of ovarian cancer: comparative values of Doppler and conventional US, CT, and MR imaging correlated with surgery and histopathologic analysis—report of the Radiology Diagnostic Oncology Group. Radiology 1999; 212:19-27.[Abstract/Free Full Text]
  46. Yamashita Y, Hatanaka Y, Torashima M, Takahashi M, Miyazaki K, Okamura H. Characterization of sonographically indeterminate ovarian tumors with MR imaging: a logistic regression analysis. Acta Radiol 1997; 38(4 pt 1):572-577.[Medline]
  47. Ghossain MA, Buy JN, Ligneres C, et al. Epithelial tumors of the ovary: comparison of MR and CT findings. Radiology 1991; 181:863-870.[Abstract/Free Full Text]



This article has been cited by other articles:


Home page
 RadiologyHome page
T. Tsujikawa, Y. Yoshida, T. Mori, T. Kurokawa, Y. Fujibayashi, F. Kotsuji, and H. Okazawa
Uterine Tumors: Pathophysiologic Imaging with 16{alpha}-[18F]fluoro-17{beta}-estradiol and 18F Fluorodeoxyglucose PET--Initial Experience
Radiology, August 1, 2008; 248(2): 599 - 605.
[Abstract] [Full Text] [PDF]

Home page
 JNMHome page
J. H. O, I. R. Yoo, S. H. Kim, H. S. Sohn, and S. K. Chung
Clinical Significance of Small Pulmonary Nodules with Little or No 18F-FDG Uptake on PET/CT Images of Patients with Nonthoracic Malignancies
J. Nucl. Med., January 1, 2007; 48(1): 15 - 21.
[Abstract] [Full Text] [PDF]

Home page
 JNMHome page
N. Pandit-Taskar
Oncologic Imaging in Gynecologic Malignancies
J. Nucl. Med., November 1, 2005; 46(11): 1842 - 1850.
[Abstract] [Full Text] [PDF]

Home page
 JCOHome page
N. Avril, S. Sassen, B. Schmalfeldt, J. Naehrig, S. Rutke, W. A. Weber, M. Werner, H. Graeff, M. Schwaiger, and W. Kuhn
Prediction of Response to Neoadjuvant Chemotherapy by Sequential F-18-Fluorodeoxyglucose Positron Emission Tomography in Patients With Advanced-Stage Ovarian Cancer
J. Clin. Oncol., October 20, 2005; 23(30): 7445 - 7453.
[Abstract] [Full Text] [PDF]

Home page
 J. Nucl. Med. Technol.Home page
M. M. Abouzied, E. S. Crawford, and H. A. Nabi
18F-FDG Imaging: Pitfalls and Artifacts
J. Nucl. Med. Technol., September 1, 2005; 33(3): 145 - 155.
[Abstract] [Full Text] [PDF]

Home page
 Br. J. Radiol.Home page
K-C Ho, K-K Ng, T-C Yen, and H-H Chou
An ovary in luteal phase mimicking common iliac lymph node metastasis from a primary cutaneous peripheral primitive neuroectodermal tumour as revealed by 18-fluoro-2-deoxyglucose positron emission tomography
Br. J. Radiol., April 1, 2005; 78(928): 343 - 345.
[Abstract] [Full Text] [PDF]

Home page
 RadioGraphicsHome page
H. K. Pannu, R. E. Bristow, F. J. Montz, and E. K. Fishman
Multidetector CT of Peritoneal Carcinomatosis from Ovarian Cancer
RadioGraphics, May 1, 2003; 23(3): 687 - 701.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
2233001850v1
223/3/780    most recent
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Fenchel, S.
Right arrow Articles by Reske, S. N.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Fenchel, S.
Right arrow Articles by Reske, S. N.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
RADIOLOGY RADIOGRAPHICS RSNA JOURNALS ONLINE